core\lock\db_record_lock_factory Class Reference

This is a db record locking factory. More...

Inheritance diagram for core\lock\db_record_lock_factory:

Public Member Functions
	__construct ($type)
	Almighty constructor.
	auto_release ()
	Auto release any open locks on shutdown.
	extend_lock (lock $lock, $maxlifetime=86400)
	Extend a lock that was previously obtained with @lock.
	get_lock ($resource, $timeout, $maxlifetime=86400)
	Create and get a lock.
	is_available ()
	Is available.
	release_lock (lock $lock)
	Release a lock that was previously obtained with @lock.
	supports_auto_release ()
	Will this lock type will be automatically released when a process ends.
	supports_recursion ()
	Multiple locks for the same resource can be held by a single process.
	supports_timeout ()
	Return information about the blocking behaviour of the lock type on this platform.

Protected Member Functions
	generate_unique_token ()
	This function generates a unique token for the lock to use.

Protected Attributes
moodle_database	$db
	$db Hold a reference to the global $DB
array	$openlocks = array()
	$openlocks - List of held locks - used by auto-release
string	$type
	$type Used to prefix lock keys

Detailed Description

This is a db record locking factory.

This lock factory uses record locks relying on sql of the form "SET XXX where YYY" and checking if the value was set. It supports timeouts, autorelease and can work on any DB. The downside - is this will always be slower than some shared memory type locking function.

Copyright

Damyon Wiese 2013

License

http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

Constructor & Destructor Documentation

__construct()

core\lock\db_record_lock_factory::__construct

(

$type

)

Almighty constructor.

Parameters

string

$type

- Used to prefix lock keys.

Implements core\lock\lock_factory.

Member Function Documentation

auto_release()

core\lock\db_record_lock_factory::auto_release

(

)

Auto release any open locks on shutdown.

This is required, because we may be using persistent DB connections.

extend_lock()

core\lock\db_record_lock_factory::extend_lock	(	lock	$lock,
			$maxlifetime = 86400 )

Extend a lock that was previously obtained with @lock.

Deprecated

since Moodle 3.10.

Parameters

lock	$lock	- a lock obtained from this factory.
int	$maxlifetime	- the new lifetime for the lock (in seconds).

Return values

boolean

- true if the lock was extended.

Implements core\lock\lock_factory.

generate_unique_token()

core\lock\db_record_lock_factory::generate_unique_token ( )

protected

This function generates a unique token for the lock to use.

It is important that this token is not solely based on time as this could lead to duplicates in a clustered environment (especially on VMs due to poor time precision).

get_lock()

core\lock\db_record_lock_factory::get_lock	(		$resource,
			$timeout,
			$maxlifetime = 86400 )

Create and get a lock.

Parameters

string	$resource	- The identifier for the lock. Should use frankenstyle prefix.
int	$timeout	- The number of seconds to wait for a lock before giving up.
int	$maxlifetime	- Unused by this lock type.

Return values

boolean

- true if a lock was obtained.

Implements core\lock\lock_factory.

is_available()

core\lock\db_record_lock_factory::is_available

(

)

Is available.

Return values

boolean

- True if this lock type is available in this environment.

Implements core\lock\lock_factory.

release_lock()

core\lock\db_record_lock_factory::release_lock

(

lock

$lock

)

Release a lock that was previously obtained with @lock.

Parameters

lock

$lock

- a lock obtained from this factory.

Return values

boolean

- true if the lock is no longer held (including if it was never held).

Implements core\lock\lock_factory.

supports_auto_release()

core\lock\db_record_lock_factory::supports_auto_release

(

)

Will this lock type will be automatically released when a process ends.

Return values

boolean

- True (shutdown handler)

Implements core\lock\lock_factory.

supports_recursion()

core\lock\db_record_lock_factory::supports_recursion

(

)

Multiple locks for the same resource can be held by a single process.

Deprecated

since Moodle 3.10.

Return values

boolean

- False - not process specific.

Implements core\lock\lock_factory.

supports_timeout()

core\lock\db_record_lock_factory::supports_timeout

(

)

Return information about the blocking behaviour of the lock type on this platform.

Return values

boolean

- True

Implements core\lock\lock_factory.

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The documentation for this class was generated from the following file:

• lib/classes/lock/db_record_lock_factory.php